This invention relates generally to an electro-hydraulic system for a work machine, and more particularly, to an electro-hydraulic system for a work machine wherein the work machine has a machinery platform moving relative to a lower frame.
Work machines, of the type having a machinery platform swung relative to the lower frame of the work machine, usually include at least one hydraulic swing motor in conjunction with a ring gear system to produce the swing or movement. Additionally, such work machines range in size, weight and load capacity, and require a substantial structure to withstand the force for swinging and moving. Additionally, a work implement is typically connected to the machinery platform. A common type of work implement has a boom with an attached stick and bucket. Some other types of work implements utilize grappling devices, or tree harvesting devices.
A typical work machine cycle includes sequentially positioning the work implement over the material to be moved, obtaining the material, swinging the implement by means of the machinery platform to a release location. The material is released and then the cycle will be repeated.
It is desirable for operators of work machines to move as much material as quickly as possible. In order to achieve this, operators will accelerate the speed at which the implement, via the machinery platform, is swung between the material obtaining and the material releasing locations. Ideally, the operator would manually reduce the speed of acceleration as the implement approaches the releasing location in order to slow down the implement enough to release the load in the proper location. However, it is quite common for an operator to keep the implement in a maximum acceleration mode until just prior to reaching the releasing location. At this point the operator would immediately put the implement into the mode for reversing the direction of the implement movement, which in effect produces a braking action on the implement movement.
The operator action of immediately going into a reverse mode to halt the movement of the implement and the machinery platform, may cause damage to the work machine. Because the implement has mass and is moving, it contains a sizable quantity of kinetic energy due to inertia of the moving elements. Also, the torque in the implement and the machinery platform during an abrupt deceleration is extremely high due to the kinetic energy. The torque may damage parts of the machinery. The torque may also produce fatigue in the ring gear system and damage the gear teeth and other components associated with swinging the machinery platform. As a consequence, all of the elements involved in swinging the machinery platform and the implement itself must be sized for the high deceleration torque which increases both component size and cost.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a method for controllably moving a machinery platform of a work machine having an electro-hydraulic system is disclosed. The work machine includes at least one swing motor configured to move the machinery platform. The changing speed of the swing motor is determined. A solenoid actuated valve is controlled in response to the determination. The solenoid actuated valve is configured to responsively produce a relief valve pilot signal. The two-way relief valve is controllably shifted in response to the inputted relief valve pilot signal. At least one of a high pressure by-pass valve and a low pressure by-pass valve is selected in response to the two-way relief valve shifting.
In a second aspect of the present invention, a method for controllably moving a machinery platform of a work machine having an electro-hydraulic system is disclosed. The work machine includes at least one swing motor configured to move the machinery platform. The changing speed of the swing motor is determined. If the determination shows the swing motor is accelerating a solenoid actuated valve is energized. If the determination shows the swing motor is decelerating the solenoid actuated valve is de-energized. A relief valve pilot signal representing the current state of the solenoid actuated valve is produced. The relief valve pilot signal is communicated with a two-way relief valve having a low pressure by-pass valve position and a high pressure by-pass valve position. If, the solenoid actuated valve is energized, the two-way relief valve is shifted to the high pressure by-pass valve position. If, the solenoid actuated valve is de-energized, the two-way relief valve is shifted to the low pressure by-pass valve position. At least one of a high pressure by-pass valve and a low pressure by-pass valve corresponding to the position of the two-way relief valve is engaged.
In a third aspect of the present invention, a work machine having an electro hydraulic system is shown. The machinery platform and the lower frame are included in the work machine, wherein the machinery platform is rotatably connected to the lower frame. A swing motor is located on the work machine. Included in the electro-hydraulic system is a controller. A detector is configured to determine the speed of the swing motor. The controller is in communication with the detector and a solenoid actuated valve. The solenoid actuated valve is included in the electro-hydraulic system. A relief valve pilot signal is produced by the solenoid actuated valve. A two-way relief valve is configured to receive the relief valve pilot signal and to move to a position in response to the relief valve pilot signal.
These and other aspects and advantages of the present invention, as defined by the appended claims, will be apparent to those skilled in the art from reading the following specification in conjunction with the drawings and the claims.